The present invention relates to an absorption refrigerator. More particularly, the invention relates to a multiple-effect absorption refrigerator in which three-stage or four-stage regenerators are connected thereto, and improves efficiency. The absorption refrigerator includes an absorption cold/hot water type.
Single-effect or double-effect absorption refrigerators having one or two stages of regenerators for steamizing the coolant by increasing temperature/pressure of the absorption fluid have conventionally occupied the main current in the industry.
When heating and concentrating an absorption fluid in a regenerator by a heat fed from outside, and reusing coolant steam generated therefrom as a heating source of the absorption fluid of the regenerator having a low inner pressure, in general, it is possible to accomplish heating and concentrating in a regenerator of a low inner pressure without supplying heat from outside. In the heating and concentrating method using such a pressure difference, the thermal efficiency is improved according as the number of regenerators is increased. More specifically, when each regenerator has an efficiency xcex7 of 65% and the heat feed quantity is a, a case with a simple regenerator gives a coolant fluid of a xc3x97xcex7=0.65a is obtained.
With two regenerators, there is available a coolant fluid of (axc3x97xcex7)+(axc3x97xcex7xc3x97xcex7)=(axc3x97xcex7)xc3x97(1+xcex7)=1.071. That is, the case with two regenerators gives a coolant fluid of 1.07/0.65≈3/2 times as large as compared with the case of a single regenerator: it suffices to use a heat feed quantity 0.65/1.07≈2/3 times for obtaining a coolant fluid in the same quantity.
For similar reasons, increasing the number of regenerators leads to a decreased heat feed quantity, thus permitting energy saving. Various triple-effect type absorption refrigerators having regenerators in three stages are proposed and industrialized for further improvement of cooling ability and efficiency (see Japanese Laid-Open Patent Publication No. 2000-171123 and Japanese Patent Publication No. 3040475).
FIG. 7 illustrates a triple-effect type absorption refrigerator proposed by Japanese Laid-Open Patent Publication No. 2000-171123. This absorption refrigerator 100 comprises an absorber 101, a low-temperature regenerator 102, a medium-temperature regenerator 103, a high-temperature regenerator 104, a condenser 105, an generator 106, heat exchangers 107 to 109, a fluid pump 110, and a coolant pump 111; wherein the high-temperature regenerator 104 has a pressure sensor 112, fluid level sensors 113 and 113xe2x80x2 are provided at the exit of the high-temperature regenerator 104 so that a revolutions controller 120 sets a basic number of revolutions for the fluid pump 110 in response to output of the pressure sensor 112, and corrects the thus set revolutions on the basis of an output signal of a fluid level sensor 113.
However, in a method of setting a basic revolutions of the fluid pump 110 on the basis of only the detected value of inner pressure of the high-temperature regenerator 104 and correcting the thus set revolutions in response to an output signal of the fluid level sensor 113, as in the conventional absorption refrigerator 100, the fluid level frequently rises up or lowers down, making it impossible to achieve a stable operation. Another problem is that, because all the regenerators are fed with the absorption fluid from the fluid pump 110 alone, an optimum feed cannot be made for the individual regenerators.
And, increasing the number of regenerators may lead to a more complicated structure and a higher cost. Furthermore, even when the number of regenerators is increased, the ratio of reducing the heating quantity is decreased, so that it is necessary to select an optimum number of regenerators taking account of the balance between the cost and the efficiency.
However, the optimum number of regenerators and the ratio of circulation of the absorption fluid in a multiple-effect type absorption refrigerator are not yet known.
The present invention is developed in view of these problems in the conventional art, and has an object to provide a reverse-cycle type multiple-effect absorption refrigerator having an optimum number of regenerators with an improved efficiency, which permits stable operation with a desired cooling performance through simple means even when there is fluctuations of load.
As a result of extensive studies on the aforementioned problems, the present inventors found that the number of regenerators permitting stable operation by a simple technique was three or four, and obtained some findings about the optimum ratio of circulation of absorption fluid meeting a number of regenerators. They thus completed the present invention.
Particularly, a first aspect of the present invention relates to a triple-effect type absorption refrigerator, and a second aspect of the invention relates to a quadruple-effect type absorption refrigerator.
More specifically, a first embodiment of the first aspect of the absorption refrigerator of the invention provides an absorption refrigerator having three-stage regenerators including a low-temperature, medium-temperature and high-temperature regenerators connected in series, comprising a diluted fluid pump feeding the low-temperature regenerator with dilute fluid obtained by causing an absorption fluid to absorb a coolant by means of an absorber; an intermediate fluid pump feeding an intermediate absorption fluid obtained through heating and concentration of the diluted absorption fluid to the medium-temperature regenerator by means of the low-temperature regenerator; a concentrated fluid pump feeding a concentrated absorption fluid obtained through heating and concentration of the intermediate absorption fluid in the medium-temperature regenerator to the high-temperature regenerator; an intermediate fluid bypass piping feeding back a part of the intermediate absorption fluid directly to the absorber so as to feed only a prescribed ratio of the intermediate absorption fluid obtained in the low-temperature regenerator to the medium-temperature regenerator by means of the intermediate fluid pump; and a concentrated fluid bypass piping feeding back a part of the concentrated absorption fluid directly to the absorber so as to feed back only a prescribed ratio of the concentrated absorption fluid obtained in the medium-temperature regenerator to the high-temperature regenerator by means of the concentrated fluid pump.
A second embodiment of the first aspect of the absorption refrigerator of the invention provides an absorption refrigerator having three-stage regenerators including a low-temperature, medium-temperature and high-temperature regenerators connected in series, comprising load detecting means detecting a load; heat feeding means feeding the high-temperature regenerator with a heat quantity as a heating source; fed heat control means controlling a heat quantity fed by the heat feeding means to the high-temperature regenerator on the basis of the load detected by the load detecting means; a diluted fluid pump feeding the low-temperature regenerator with diluted fluid obtained by causing an absorption fluid to absorb a coolant by means of an absorber; an intermediate fluid pump feeding an intermediate absorption fluid obtained through heating and concentration of the diluted absorption fluid to the medium-temperature regenerator by means of the low-temperature regenerator; a concentrated-fluid pump feeding a concentrated absorption fluid obtained through heating and concentration of the intermediate absorption fluid in the medium-temperature regenerator to the high-temperature regenerator; an intermediate fluid bypass piping feeding back a part of the intermediate absorption fluid directly to the absorber so as to feed back only a prescribed ratio of the intermediate absorption fluid obtained in the low-temperature regenerator to the medium-temperature regenerator by means of the intermediate fluid pump; a concentrated fluid bypass piping feeding back a part of the concentrated absorption fluid directly to the absorber so as to feed back only a prescribed ratio of the concentrated absorption fluid obtained in the medium-temperature regenerator to the high-temperature regenerator by means of the concentrated fluid pump; and revolutions control means which controls the revolutions of the diluted fluid pump, the intermediate fluid pump and the concentrated fluid pump so as to feed only a prescribed ratio of the intermediate absorption fluid obtained in the low-temperature regenerator, to feed only a prescribed ratio of the concentrated absorption fluid obtained in the medium-temperature regenerator, and to feed a prescribed ratio of the diluted absorption fluid having absorbed the coolant in the absorber from the absorber to the low-temperature regenerator.
In the first aspect of the absorption refrigerator of the invention, it is preferable that the ratio of an initial rated circulation quantity is selected so that the prescribed ratio of the intermediate absorption fluid fed by the intermediate fluid pump to the medium-temperature regenerator is within a range of from 50 to 98% of the feed quantity of the low-temperature regenerator, that the ratio of an initial rated circulation quantity is selected so that the prescribed ratio of the concentrated absorption fluid fed by the concentrated fluid pump to the high-temperature regenerator is within a range of from 50 to 98% of the feed quantity of the medium-temperature regenerator, and that the ratio of an initial circulation quantity is selected so that the feed quantity of the concentrated fluid pump during rated operation is within a range of from 30 to 90% of the feed quantity of the diluted fluid pump.
In the second embodiment of the first aspect of the invention, it is preferable that the absorption refrigerator has steam temperature detecting means detecting the temperature of coolant steam generated in the high-temperature regenerator; the revolutions control means performs control so as to increase the revolutions of the concentrated fluid pump when the temperature of the coolant steam detected by the steam temperature detecting means is over a prescribed temperature; and the revolutions control means performs control so as to reduce the revolutions when the temperature of the coolant steam detected by the steam temperature detecting means is under a prescribed temperature.
Also, in the second embodiment of the first aspect of the absorption refrigerator of the invention, it is preferable that the absorption refrigerator has steam pressure detecting means detecting the pressure of coolant steam generated in the high-temperature regenerator; the revolutions control means performs control so as to increase the revolutions of the concentrated fluid pump when the pressure of the coolant steam detected by the steam pressure detecting means is over a prescribed pressure; and the revolutions control means performs control so as to decrease the revolutions of the concentrated fluid pump when the pressure of the coolant steam detected by the steam pressure detecting means is under the prescribed pressure.
Furthermore, in the second embodiment of the first aspect of the invention, it is preferable that the absorption refrigerator has drain temperature detecting means detecting the temperature of coolant drain after heating the medium-temperature generator of the coolant steam, fed as a heating source for heating and concentrating the intermediate absorption fluid from the high-temperature regenerator to the medium-temperature regenerator; and the revolutions control means performs control so as to increase the revolutions of the concentrated fluid pump when the temperature of the coolant drain detected by the drain temperature detecting means is over a prescribed temperature. In this case, it is more preferable that, when the temperature of the coolant drain detected by the drain temperature detecting means is under the prescribed temperature, the revolutions control means performs control so as to reduce the revolutions of the concentrated fluid pump.
Also, in the second embodiment of the first aspect of the absorption refrigerator of the invention, it is preferable that the absorption refrigerator has a fluid level detecting means detecting the level of the absorption fluid in the high-temperature regenerator; the revolutions control means performs control so as to reduce the number of revolutions of the concentrated fluid pump when the level of the absorption fluid in the high-temperature regenerator detected by the fluid level detecting means is over an upper limit level, and increases the number of revolutions of the concentrated fluid pump when level of the absorption fluid in the high-temperature regenerator detected by the fluid level detecting means is under a low limit level. In this case it is more preferable that the absorption refrigerator further comprises an alarm and emergency stop means which, when the level of the absorption fluid in the high-temperature regenerator detected by the fluid level detecting means is under an emergency set value set for safety, gives an alarm, and stop feeding of heat by the heat feeding means. It is also preferable that, when the revolutions control means adjusts the number of revolutions of the concentrated fluid pump in response to the result of detection by the fluid level detecting means, the number of revolutions of the concentrated fluid pump is changed stepwise within a predetermined range of revolutions; that, when the revolutions control means adjusts the number of revolutions of the concentrated fluid pump in response to the result of detection by the fluid level detecting means, the number of revolutions of the concentrated fluid pump is changed continuously; or that, when the revolutions control means adjusts the number of revolutions of the concentrated fluid pump in response to the result of detection by at least one of the steam temperature detecting means, the steam pressure detecting means, the drain temperature detecting means and the fluid level detecting means, control is performed so as to simultaneously adjust also the number of revolutions of at least any one of the diluted fluid pump and the intermediate fluid pump. In this case, the revolutions control means may previously set combinations of a number of revolutions of the concentrated fluid pump, the simultaneously controlled diluted fluid pump and/or the intermediate fluid pump, and a combination may be appropriately selected from these combinations.
A second aspect of the absorption refrigerator of the invention provides an absorption refrigerator having four-stage regenerators including a low-temperature, a medium-temperature, a second medium-temperature and a high-temperature regenerators connected in series, comprising load detecting means detecting the load; heat feeding means feeding a heat quantity as a heating means to the high-temperature regenerator; fed heat control means controlling a heat quantity fed by the heat feeding means to the high-temperature regenerator on the basis of the load detected by the load detecting means; a diluted fluid pump feeding a diluted absorption fluid obtained through absorption of a coolant by an absorption fluid by means of an absorber to the low-temperature regenerator; an intermediate fluid pump feeding an intermediate absorption fluid obtained by heating and concentrating the diluted absorption fluid in the low-temperature regenerator to the medium-temperature regenerator; a second intermediate fluid pump feeding the second intermediate absorption fluid obtained by heating and concentration the intermediate absorption fluid in the medium-temperature regenerator to the second medium-temperature regenerator; a concentrated fluid pump feeding the concentrated absorption fluid obtained through heating and concentration of the second intermediate absorption fluid in the second medium-temperature regenerator to the high-temperature regenerator; an intermediate fluid bypass piping feeding back a part of the intermediate absorption fluid directly to the absorber so as to feed a prescribed ratio of the intermediate absorption fluid obtained in the low-temperature regenerator to the medium-temperature regenerator by means of the intermediate fluid pump; a second intermediate fluid bypass piping feeding back a part of the second intermediate absorption fluid directly to the absorber so as to feed a prescribed ratio of the second intermediate absorption fluid obtained in the medium-temperature regenerator to the second medium-temperature regenerator by means of the second intermediate fluid pump; a concentrated fluid bypass piping feeding back a part of the concentrated absorption fluid directly to the absorber so as to feed a prescribed ratio of the concentrated absorption fluid obtained in the second medium-temperature generator to the high-temperature regenerator by means of the concentrated fluid pump; and revolutions control means controlling the number of revolutions of the diluted fluid pump, the intermediate fluid pump, the second intermediate fluid pump and the concentrated fluid pump so as to feed a prescribed ratio of the intermediate absorption fluid obtained in the low-temperature regenerator to the medium-temperature regenerator, feed a prescribed ratio of the second intermediate absorption fluid obtained in the medium-temperature regenerator to the second medium-temperature regenerator, feed only a prescribed ratio of the concentrated absorption fluid obtained in the second medium-temperature regenerator, and feed a prescribed ratio of the diluted absorption fluid having absorbed the coolant by means of the absorber from the absorber to the low-temperature regenerator.
In the second aspect of the absorption refrigerator of the invention, it is preferable that the ratio of an initial rated circulation quantity is selected so that the prescribed ratio of the intermediate absorption fluid fed by the intermediate fluid pump to the medium-temperature regenerator is within a range of from 50 to 98% of the feed quantity of the low-temperature regenerator; that the ratio of an initial rated circulation quantity is selected so that the prescribed ratio of the second intermediate absorption fluid fed by the intermediate fluid pump to the second medium-temperature regenerator is within a range of from 50 to 98% of the feed quantity of the medium-temperature regenerator; that the ratio of an initial rated circulation quantity is selected so that the prescribed ratio of the concentrated absorption fluid fed by the concentrated fluid pump to the high-temperature regenerator is within a range of from 50 to 98% of the feed quantity of the second medium-temperature regenerator; or that the ratio of an initial circulation quantity is selected so that the feed quantity of the concentrated fluid pump during rated operation is within a range of from 30 to 90% of the feed quantity of the diluted fluid pump.
Also, in the second aspect of the absorption refrigerator of the invention, it is preferable that the absorption refrigerator has steam temperature detecting means detecting the temperature of coolant steam generated in the high-temperature regenerator; the revolutions control means performs control so as to increase the revolutions of the concentrated fluid pump when the temperature of the coolant steam detected by the steam temperature detecting means is over a prescribed temperature; and the revolutions control means performs control so as to reduce the revolutions when the temperature of the coolant steam detected by the steam temperature detecting means is under a prescribed temperature.
Furthermore, in the second aspect of the absorption refrigerator of the invention, it is preferable that the absorption refrigerator has steam pressure detecting means detecting the pressure of coolant steam generated in the high-temperature regenerator; the revolutions control means performs control so as to increase the revolutions of the concentrated fluid pump when the pressure of the coolant steam detected by the steam pressure detecting means is over a prescribed pressure; and the revolutions control means performs control so as to decrease the revolutions of the concentrated fluid pump when the pressure of the coolant steam detected by the steam pressure detecting means is under the prescribed pressure.
Moreover, in the second aspect of the absorption refrigerator of the invention, it is preferable that the absorption refrigerator has drain temperature detecting means detecting the temperature of coolant drain after heating the second medium-temperature regenerator of the coolant steam, fed as a heating source for heating and concentrating the second intermediate absorption fluid from the high-temperature regenerator to the second medium-temperature regenerator; and a second temperature detecting means detecting the coolant drain temperature after heating the medium-temperature regenerator of coolant steam fed as a heating source for heating and concentrating the intermediate absorption fluid from the second medium-temperature regenerator to the medium-temperature regenerator; and, when at least one of the coolant drain temperatures detected by the drain temperature detecting means and the second drain temperature detecting means becomes over the prescribed temperature thereof, the revolutions control means performs control so as to increase the number of revolutions of the concentrated fluid pump.
In this case, it is preferable that, when at least one of the coolant drain temperatures detected by the drain temperature detecting means and the second drain temperature detecting means becomes under the prescribed temperature thereof, the revolutions control means performs control so as to reduce the number of revolutions of the concentrated fluid pump; or that the absorption refrigerator has a fluid level detecting means detecting the level of the absorption fluid in the high-temperature regenerator; the revolutions control means performs control so as to reduce the number of revolutions of the concentrated fluid pump when the level of the absorption fluid in the high-temperature regenerator detected by the fluid level detecting means is over an upper limit level, and increases the number of revolutions of the concentrated fluid pump when the level of the absorption fluid in the high-temperature regenerator detected by the fluid level detecting means is under a low limit level. In addition, it is also preferable that the absorption refrigerator comprises an alarm and emergency stop means which, when the level of the absorption fluid in the high-temperature generator detected by the fluid level detecting means is under emergency set value for safety, gives an alarm, and stop feeding of heat by the heat feeding means; that, when the revolutions control means adjusts the number of revolutions of the concentrated fluid pump in response to the result of detection by the fluid level detecting means, the number of revolutions of the concentrated fluid pump is changed stepwise within a predetermined range of revolutions; that, when the revolutions control means adjusts the number of revolutions of the concentrated fluid pump in response to the result of detection by the fluid level detecting means, the number of revolutions of the concentrated fluid pump is changed continuously; or that, when the revolutions control means adjusts the number of revolutions of the concentrated fluid pump in response to the result of detection by at least one of the steam temperature detecting means, the steam pressure detecting means, the drain temperature detecting means, the second drain temperature detecting means and the fluid level detecting means, control is performed so as to simultaneously adjust also the number of revolutions of at least any one of the diluted fluid pump, the intermediate fluid pump and the second intermediate fluid pump. It is also preferable that the revolutions control means previously sets combinations of a number of revolutions of the concentrated fluid pump, the simultaneously controlled diluted fluid pump, the intermediate fluid pump, and/or the second intermediate fluid pump, and a combination can be appropriately selected from these combinations.
Also, in the second aspect of the absorption refrigerator of the invention, the absorption refrigerator may have at least one of a low-temperature heat exchanger which heats the diluted absorption fluid fed from the diluted fluid pump and feeds the same to the low-temperature regenerator, a medium-temperature heat exchanger which heats the intermediate absorption fluid fed from the intermediate fluid pump and feeds the same to the medium-temperature regenerator, a second medium-temperature heat exchanger which heats the second intermediate absorption fluid fed from the second intermediate fluid pump and feeds the same to the second medium-temperature regenerator, and a high-temperature heat exchanger which heats the concentrated absorption fluid fed from the concentrated fluid pump and feeds the same to the high-temperature regenerator.
Furthermore, in the second aspect of the absorption refrigerator of the invention, the absorption refrigerator may comprise a second high-temperature steam return piping feeding the coolant steam from the high-temperature regenerator as a heating source to the medium-temperature regenerator; and a steam piping change-over valve provided in the second high-temperature steam return piping; wherein the coolant steam from the high-temperature regenerator is fed as a heating source to the second temperature regenerator and the medium-temperature regenerator. In this case, the absorption refrigerator may comprise a branched coolant drain piping causing the second medium-temperature regenerator and the medium-temperature regenerator to communicate with each other; and a drain piping change-over valve provided in the branched drain piping; or the steam piping change-over valve may be a safety valve which opens when a pressure of over a value set for safety is applied.
Also, in the second aspect of the absorption refrigerator of the invention, the drain piping change-over valve may be controlled so as to open when the temperature in the high-temperature regenerator becomes over a value set for safety.
Further, in the second aspect of the absorption refrigerator of the invention, it is preferable that only the second medium-temperature regenerator, or both the second medium-temperature regenerator and the medium-temperature regenerator comprise pressure vessels.
Still, in the absorption refrigerator of the invention, the high-temperature regenerator may have a steam-fluid separator that separates generated coolant steam and the absorption fluid; or, the high-temperature regenerator may be a once-through boiler.
In the absorption refrigerator of the invention, for example, the coolant is water, and the absorption fluid mainly comprises lithium bromide.
In the absorption refrigerator of the present invention, having the configuration as described above, it is possible to optimize the circulation quantity of the absorption fluid to the individual regenerators by adjusting the number of revolutions of each pump, thus to improve the efficiency, and ensure stable operation with a desired cooling ability even when there is fluctuation of load.